<!doctype html>
<style>
  body {
    font-size: 96px;
    font-family: Arial;
  }

  #outer {
    background: #eee;
  }

  #wrap {
    display: inline-block;
    height: 10px;
  }

</style>

<body>
  <div id="outer">
    X
    <div id="wrap">Y</div>
  </div>
</body>
